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On Fri, Oct 02, 2015 at 12:27:16PM +0300, Jarkko Nikula wrote:
> On 10/01/2015 11:37 PM, Wolfram Sang wrote:> >> >>This is for discussion so I didn't cc stable@vger.kernel.org yet. I was> >>thinking would it work if we'd keep the stable name but have an another> >>symlink in /sys/bus/i2c/devices/ that uses "x-00yz" name. However this> >>feels ill-use of devices directory and probably causes more troubles> >>elsewhere.> >> >Do you foresee troubles already? I am still in favour of a symlink.> >> I haven't looked at this for a while but one problem was that devices/> directory belongs to private structure of struct bus_type and in order to> create a symlink there it needs to done in drivers/base/bus.c:> bus_add_device() which felt quite hackish to me.
This is just a quick prototype and untested; but I did something similar
in the i2c-mux code:
Shouldn't something like this be enough?

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Hi
On 10/10/2015 12:47 AM, Wolfram Sang wrote:
> On Fri, Oct 02, 2015 at 12:27:16PM +0300, Jarkko Nikula wrote:>> On 10/01/2015 11:37 PM, Wolfram Sang wrote:>>> Do you foresee troubles already? I am still in favour of a symlink.>>>>> I haven't looked at this for a while but one problem was that devices/>> directory belongs to private structure of struct bus_type and in order to>> create a symlink there it needs to done in drivers/base/bus.c:>> bus_add_device() which felt quite hackish to me.>> This is just a quick prototype and untested; but I did something similar> in the i2c-mux code:>> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c> index 5f89f1e3c2f24f..715dca57ba68fd 100644> --- a/drivers/i2c/i2c-core.c> +++ b/drivers/i2c/i2c-core.c> @@ -970,13 +970,15 @@ static void i2c_dev_set_name(struct i2c_adapter *adap,> {> struct acpi_device *adev = ACPI_COMPANION(&client->dev);>> - if (adev) {> - dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));> - return;> - }> -> dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),> i2c_encode_flags_to_addr(client));> +> + if (adev) {> + char symlink_name[256];> +> + snprintf(symlink_name, sizeof(symlink_name), "i2c-%s", acpi_dev_name(adev));> + sysfs_create_link(&client->dev.kobj, &adap->dev.kobj, symlink_name);> + }> }>> /**>> Shouldn't something like this be enough?>
Not really. It would create the symlink under the device not under
/sys/bus/i2c/devices/. Please note the sysfs_create_link() must be
called after device_register(). I moved the symlink creation into
i2c_new_device() for the example below.
Now:
/sys/bus/i2c/devices/i2c-ATML3432:00 ->
../../../devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-9/i2c-ATML3432:00
After modified patch:
/sys/bus/i2c/devices/9-004c ->
../../../devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-9/9-004c
which has now the symlink pointing to adapter
/sys/devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-9/9-004c/
i2c-ATML3432:00 -> ../../i2c-9
We would need a following symlink but I didn't figure out how to do it
without touching drivers/base/bus.c.
/sys/bus/i2c/devices/i2c-ATML3432:00 -> 9-004c
Symlinks there are added/removed by using &bus->p->devices_kset->kobj
where p is a private for driver core only.